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View Full Version : Help with new scope base holes in a Remington SS 700



jlcprec
02-06-2008, 10:52 PM
Today I had to retap the scope base holes in a stainless steel 700. They needed to be for 8-40 screws. Does anyone have any easier way to do this?
I was very unhappy doing this. The action evidently has been hardened somewhat. (I didn't think they were.) They drilled extremely hard and tapping them was scary. I got it done, but I went no deeper with the tap than I had to.

Dennis Sorensen
02-06-2008, 10:58 PM
I haven't had to do it to a 700 but in cases like that I always drilled through and using a new tapered tap and a new plug tap worked back and forth with each until the hole was tapped right through.. I have found a water soluble lubricant called ANCHORLUBE G-771 (Ohio) to work very well. I tap with the tapered starter tap until it gets fairly tight, then I will run the plug tap in until it gets fairly tight, then the starter tap again and the plug tap again, etc... and I do all of this in the drill press... much less chance of tap breakage..

Dave Short
02-06-2008, 11:14 PM
A word of caution regarding tapping the "difficult to machine" stainless steels: Any more backing up and breaking of the chip than absolutely necessary will work harden the material. I won't be too specific as to the tap and lube, but I will say use a high performance tap and a good lube...........the Anchor Lube is good stuff (not to mention that it looks like it ought to be mint flavored), but I prefer something sulferized, or Castrol's Safety Draw (mix the stuffin' out of it before use).

-Dave-:)

4Mesh
02-06-2008, 11:14 PM
It's unfortunate you didn't ask here before doing this. Yes, the Remington SS receivers are harder'n the hubs of hell, and tough.

The thing is, I'd never have gone to 8-40, I'd have done 8-32 or 10-32. I like it when I can actually get screws at the hardware store. The person who came up with the idea of a bastard threads on guns should be taken to the town square and hung until death.

I know, somebody here who's an "Engineer" is gonna start quoting to me the strengths of one screw vs another. Well, I mean, if somebody wanted em stronger, why not just use 1/2-20's and get it over with. At least they sell em at the store.

I use nice taps for that sort of thing. Emuge and Guhring are names I stick by when doing hard materials. Emuge seems to cost a little more, but I have an Emuge 10-32 tap that I've used for about 5 years in tough materials. Now, that tap 5 years ago was around $35, but it was money well spent. It finally gave up when I attempted to tap some 4340 that was really hard and the lead flutes are broke. I tried hand tapping with it and it's a production tap. It should have been turning faster and most likely would never have broken. It still taps aluminum as nice as any tap brand new, and that's no exaggeration. What a tool. I still run it in the mill at high speed on aluminum parts and never give it a thought. I do not know if Emuge or Guhring sell taps in 8-40 though. If they do, get one made for stainless and it'll go through that receiver like it's nylon.

I also have Ghuring taps that I keep in my personal stash for tough tapping projects. When I want something to turn out nice, I grab those. I pick em up from MSC when there's a sale on em. Otherwise, they seem really expensive.

4Mesh
02-06-2008, 11:24 PM
I almost forgot,

As Dave mentioned about the work hardening, there's an important thing to remember too. That PH SS can get ungawdly hard when drilling. When the drill starts to sound like it's really not having a good time, you can pretty much forget running a tap. Recently I tried something similar with a Caliper I bought. I was making a new measuring device for us at the range and wanted to take a new 12" Caliper and do some drilling and tapping on the jaws. Well, to make a long story short, drilling the holes with a HSS drill only worked for one hole. When that hole was done, it was all over but the cryin. No more holes got drilled, and there was no way on earth to tap the holes. I got one done. The one that hardedned would not allow a tap in and I mean it would not even start. All I heard was a little tink... end of tapping operation...

Drill the holes with a VERY good drill. I'd suggest a carbide drill if it were me. That way it won't work harden. Ordering one for that purpose would be a good investment if you do this sort of thing often. Your taps will life a lot longer if all they do is tap the medium hard material. Once it's really hard from a drill smearing it around, forget it.

ps.. I tig welded my parts to the caliper after the tap idea failed. Whod'a thunk a cheapo import caliper would be material that tough...

Here's a couple links for ya.
http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000044372114 Item# 02776482

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=9115033&PMT4NO=0 Item# 63266381

Either of these two taps would have laughed at that stainless material.

Zebra13
02-07-2008, 12:04 AM
The thing is, I'd never have gone to 8-40, I'd have done 8-32 or 10-32. I like it when I can actually get screws at the hardware store. The person who came up with the idea of a bastard threads on guns should be taken to the town square and hung until death.

I know, somebody here who's an "Engineer" is gonna start quoting to me the strengths of one screw vs another. Well, I mean, if somebody wanted em stronger, why not just use 1/2-20's and get it over with. At least they sell em at the store.



4Mesh,

Amen, my brother! I went on a two county pilgrimage for an 8-40 screw this week...had a better chance of finding Hoffa or OJ's other glove.

Justin

Dave Short
02-07-2008, 06:39 AM
The thing is, I'd never have gone to 8-40, I'd have done 8-32 or 10-32. I like it when I can actually get screws at the hardware store. The person who came up with the idea of a bastard threads on guns should be taken to the town square and hung until death.

I know, somebody here who's an "Engineer" is gonna start quoting to me the strengths of one screw vs another. Well, I mean, if somebody wanted em stronger, why not just use 1/2-20's and get it over with. At least they sell em at the store.



4Mesh,

Amen, my brother! I went on a two county pilgrimage for an 8-40 screw this week...had a better chance of finding Hoffa or OJ's other glove.

Justin

The source for these screws is Brownell's. A long time ago I searched all of the industrial fastner suppliers for them, and they all said the same thing: "The -40's are gun screws, we don't handle them".

-Dave-:)

jlcprec
02-07-2008, 11:27 PM
It wasn't my idea to use 8-40 screws. I was handed the scope mount (a big tapered picanny type rail) and the screws, and asked to do the job. I thought the Remingtons were made from 416 stainless, not PH types. I drilled out the original threads in 3 steps, the first couple of bits would complain a little, but the last one drilled good. I was using my mill for all the drilling and started the tap (by hand) in the mill also, so everything stayed straight. I was using a brand new plug tap from MSC. They only had 2 choices in the 8-40, both being imports. Believe me, I would have bought the best one I could get. Perhaps I should have tried Brownell's, but I needed some other stuff from MSC.

Riflemeister
02-08-2008, 11:04 AM
On the issue of 8-32 vs 8-40 threads on a receiver, the 8-40 is a shallower thread depth than the 8-32 which in this instance of a really tough to tap receiver should be a real advantage. Additionally, any gunsmith having to go back and work on the gun would be expecting either a 6-48 or 8-40 thread on the scope mounting holes. Its not nice to lay landmines for your fellow gunsmiths.

Zebra13
02-08-2008, 01:18 PM
The source for these screws is Brownell's. A long time ago I searched all of the industrial fastner suppliers for them, and they all said the same thing: "The -40's are gun screws, we don't handle them".

-Dave-:)

Dave,

I new Brownell's had em', but I needed one right now and was hoping against hope that I could find one. Alas...no go.

I think Brownell's has a "Gunsmiths assortment" screw kit that I will buy for just such situations. Have you, or anybody else gone that route? If so, how did it work out.

Thanks,
Justin

4Mesh
02-08-2008, 01:24 PM
Riflemeister,

I"m not sure what land mine you mean. What would it matter to the next gunsmith what screws were in there? Isn't that what gunsmiths do? I mean, it's not like they throw thier arms in the air when they see it's not a 6-40 anymore, why would they care if it was a 8-32, 8-36 or 8-40? Any of them is not what it used to be.

At least in the case of 8-36 or 8-32 you can actually buy the taps and there's even a chance a guy might have one on the shelf already. Screws can be purchases and the underside of the heads modified if need be (though I don't). Unbrako or Holochrome QUALITY screws are actually available, not like the chinsy things you can buy in 8-40.

I'd make a bet with you that in full hard 17-4SS, a Emuge 8-32 tap (made for high nickel alloys) will tap with less effort than the 8-40 taps you can buy at Brownells or MSC, McMaster, Grainger, etc. When that material is at 46c, you better have a Deluxe quality tap to stick threads in.

When working on CM Remington receivers, an Enco import tap will work fine.

chuck furniss
02-08-2008, 08:28 PM
I have drilled and tapped many stainless receivers and barrels over the years and have found that good cobalt drill bits do a great job and are much cheaper than carbide.Also I prefer to use high carbon taps over high speed steel.They are easier to get out if you break one and stay sharp longer. Break off a high speed steel tap below the surface and tou are in deep trouble.

Chuck.

Spott3r
02-09-2008, 02:44 AM
..parting tool on one of Shiraz's new Kreiger barrels.

Man, it was like a butter knife!

Gordy was kind of standing back because he said the feed rate was kinda quick..sure was..lickety-split.

:D

Bill Myers
02-09-2008, 10:42 AM
I have built several Titanium actions & the bar stock has a 46c rockwell,so the holes need to be drilled & tapped,I used solid carbide in 8/32 tap & carbide drills.The carbide tap is 80.00,but thats cheap in the long run. BILL